Systems for controlling operation of a vehicle based on user's intention of operation are in practical use. In such systems, user's intention is determined based on variations in accelerator pedal positions and brake pedal positions, and operation of a vehicle is performed based on the determined user's intention. An example of such a system is proposed in JP-A-2002-114118. In this system, user's intention of braking is determined based on whether the user steps on a brake pedal. User's intention of acceleration is determined based on whether the user increases pressure on an accelerator pedal, and user's intention of deceleration is determined based on whether the user releases the accelerator pedal. With this configuration, the control of the vehicle operation is automatically adjusted without annoying the user.
More and more functions may become available in vehicles for users' convenience. However, users may have more loads for using the functions and the operability of the vehicles may decrease. This declines the benefit of having advanced functions in the vehicles. For example, a user needs to perform some kind of operation in order to get the functions work in the above-described system. To determine user's intention of braking, acceleration or deceleration, user's operation of the braking pedal or the acceleration pedal is required. Therefore, the operability of the vehicle may decrease as the number of functions increases.